1. Field of the Invention
The present invention relates to the field of furnaces for the combustion of waste materials and in particular pertains to the organization of air flow throughout such a furnace so that moist waste materials may be burned in a self-sustaining combustion without the aid of additional fuels.
2. Description of the Prior Art
The prior art has been concerned with the design and operation of furnaces capable of combusting moist waste materials, such as livestock excrement from breeding farms or paper sludge discarded by pulp mills. However, such furnaces incorporate several disadvantages such as, excessive cost for supplementary fuels necessary to sustain combustion, inability to satisfactorily eliminate odor, and the absence of suitable waste heat recovery, all of which problems have never been simultaneously resolved by a single furnace design. The common property of the waste materials intended for disposal within such furances is that such materials are themselves combustible but retain a large quantity of trapped moisture and are therefore difficult to use in a self-sustaining combustion unless a large quantity of additional fuel, such as gas or oil, is added. Furthermore, it is common that when such waste materials are burned, a large amount of offensive odor and smoke is discharged with deleterious psychological and physiological effects in the proximity of the discharge. In addition, the high temperature exhaust gas from such a furnace is commonly discharged into the atmosphere and lost without recovering the thermal energy content therein, or if a heat exchanger is provided for such recovery, an additional exhaust fan is required in order to make up for the drop of temperature in the exhaust gas caused thereby, which drop otherwise would interfere with proper exhaust draft from such a furnace.
What is needed then is a waste furnace for the combustion of moist animal excrement or paper sludge which is capable of containing a self-sustaining combustion in which the waste material is heated, dried, gasified, fired and combusted without the use of any supplemental fuel in such a manner that gases having an odor are largely eliminated and exhaust energy recovered without necessitating the use of an additional exhaust fan. The present invention simultaneously achieves all of these results.